1. Field of the Invention
The present invention relates to an electric toothbrush.
2. Description of the Related Art
There is known an electric toothbrush of a type for toothbrushing (removing plaque) by placing a high speed vibration brush against a tooth surface. In this type of the electric toothbrush, various driving mechanisms and driving methods have been proposed for an improvement in plaque removing power and an improvement in the sense of medical treatment.
Japanese Patent Application National Publication (Laid-Open) No. 6-510675 (WO92/16160) discloses a configuration which vibrates a lever arm provided with a brush to the right and the left at a frequency substantially equivalent to a resonance frequency in a magnetically driven electric toothbrush. Japanese Patent Application National Publication (Laid-Open) No. 2007-514397 (WO2005/058188) discloses a configuration which periodically changes amplitude of a brush head in a range of 5 to 30% by changing a driving frequency centered on a resonance frequency which is deviated by approximately 0 to 5 Hz from a resonance frequency of a toothbrush. Furthermore, Japanese Patent Application Laid-Open (JP-A) No. 7-116027 (U.S. Pat. No. 5,493,747) discloses a configuration which controls a frequency of a brush by changing the number of rotation of a motor on the basis of a detection result of toothbrushing pressure.